Wireless IC device and manufacturing method thereof

ABSTRACT

A wireless IC device includes a radiation plate, a wireless IC chip, and a substrate provided with a feed circuit that includes a resonant circuit and/or the matching circuit including an inductance element and that is electromagnetically coupled to the radiation plate. The substrate is made of a resin material. A recess is provided in a first main surface of the substrate. The substrate is provided with a wiring electrode arranged along a bottom surface and an inner circumferential surface of the recess and the first main surface of the substrate and electrically connected to the feed circuit, and a wedge member made of a different material from the resin material and extending between the bottom surface of the recess and a second main surface of the substrate spaced apart from the wiring electrode. The wireless IC chip is mounted in the recess and coupled to the wiring electrode.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless IC device and amanufacturing method thereof. More specifically, the present inventionrelates to a wireless IC device, such as a non-contact wireless ICmedium or a non-contact wireless IC tag, for example, used in an RFID(radio frequency identification) system, and a manufacturing methodthereof

2. Description of the Related Art

Wireless IC devices including a module in which a wireless IC chip ismounted on a substrate and a radiation plate have been developed. Insuch a wireless IC device, a recess is provided in the substrate and thewireless IC chip is mounted in the recess.

Japanese Unexamined Patent Application Publication No. 2004-319848discloses a semiconductor apparatus manufactured by forming a wiringsubstrate by bonding copper bumps 116 a and 118 a and wiring patterns117 and 119 to both surfaces of a resin substrate 110 with prepregs 120therebetween as shown in a sectional view in FIG. 12A, counterboring apredetermined location of the wiring substrate so as to form a recess122 as shown in a sectional view in FIG. 12B, electrically connecting asemiconductor chip 130 to an edge surface A of the copper bump 116 bexposed on the bottom surface of the recess 122 as shown in a sectionalview in FIG. 12C so as to mount the semiconductor chip 130 in the recess122, and then filling the recess 122 with a resin 124 so as to seal thesemiconductor chip 130.

If a multilayer resin substrate is formed and then subjected tocounterboring, which is a mechanical process, as described in JapaneseUnexamined Patent Application Publication No. 2004-319848, the number ofsteps is increased and a counterboring apparatus is required. Thus, themanufacturing cost is increased.

In addition, since a first main surface of the resin substrate havingthe recess and a semiconductor chip are connected, it is difficult toprovide wiring on the inner circumferential surface of the recess formedby counterboring. This makes it difficult to provide wiring having theshortest possible length and wiring must be routed such that the lengththereof is increased. For example, wiring must be routed from the bottomsurface of the recess 122 to a wiring pattern 117 on a second mainsurface of the multilayer resin substrate via the copper bump 116 b andfrom the wiring pattern 117 on the second main surface to the first mainsurface via the copper bumps 116 a and 118 a.

When the wiring is routed as described above, an unnecessary inductorcomponent or capacitor component occurs in a portion of the wiring. Thisdegrades the electrical properties and/or complicates the manufacturingprocess, thereby causing reduced yield, for example. Thisdisadvantageously increases the manufacturing cost.

SUMMARY OF THE INVENTION

To overcome the problems described above, preferred embodiments of thepresent invention provide a wireless IC device which is manufactured ata reduced cost and which prevents degradation of electrical properties,and a manufacturing method thereof.

A wireless IC device according to a first preferred embodiment of thepresent invention includes a radiation plate, a wireless IC chip, and asubstrate on which the wireless IC chip is mounted, the substrate beingprovided with a feed circuit, the feed circuit including a resonantcircuit and/or a matching circuit, the resonant circuit and/or thematching circuit including an inductance element, the feed circuit beingelectromagnetically coupled to the radiation plate. The substrate ispreferably made of a resin material and includes a recess in a firstmain surface of the substrate. The substrate is provided with a wiringelectrode arranged along a bottom surface and an inner circumferentialsurface of the recess and the first main surface of the substrate, thewiring electrode being electrically connected to the feed circuit, and awedge member made of a material that is different from the resinmaterial, the wedge member extending between the bottom surface of therecess and a second main surface of the substrate apart from the wiringelectrode. The wireless IC chip is mounted in the recess and coupled tothe wiring electrode.

With the above-mentioned configuration, the wireless IC chip ispreferably electrically connected to the feed circuit via the wiringelectrode, or electromagnetically coupled to the feed circuit via aninsulating material, for example. The wedge member may preferably bemade of a material that is different from that of the substrate so thatthe wedge member is deformed in a different manner from that of thesubstrate, and thus, prevents the deformation of the substrate near therecess.

With the above-mentioned configuration, the recess is easily formed inthe substrate made of the resin material by pressing an area of thefirst main surface of the substrate that will become the recess. Bysimultaneously pressing the wiring electrode provided in advance inareas that will become the bottom surface and the inner circumferentialsurface of the recess, the wiring electrode extends along the bottomsurface and the inner circumferential surface of the recess.

If a resin material is pressed and thus deformed, the deformed resinmaterial may be deformed such that the deformed portion is restored toits original shape, that is, in a direction opposite to a direction inwhich the resin material has been deformed by the press. In such a case,the wedge member extending between the bottom surface of the recess andthe second main surface of the substrate prevents deformation of thesubstrate near the recess.

The wedge member is preferably provided separately from the wiringelectrode to which the wireless IC chip is electrically connected. Thatis, the wedge member is not electrically connected to the wireless ICchip. Therefore, the wedge member does not degrade the electricalproperties of the wireless IC chip.

In addition, the first main surface of the substrate and the wireless ICchip are connected via a wiring electrode having the shortest possiblelength. This prevents the occurrence of an unnecessary inductorcomponent or capacitor component in the portion of the wiring anddegradation of the electrical properties thereby.

The wedge member is preferably formed by filling a through hole passingthrough the substrate with a conductive material.

In this case, the wedge member is easily formed. For example, the wedgemember may be formed using the same or substantially the same materialas that of the wiring via conductor passing through the substrate,simultaneously with the via conductor.

The feed circuit is preferably provided on the first main surface of thesubstrate and/or on the second main surface thereof.

In this case, a pattern of the feed circuit is preferably provided onboth main surfaces of the substrate and the patterns on both the mainsurfaces are preferably connected through a via conductor. Thus, even ifthe feed circuit is downsized, it is sufficiently electromagneticallycoupled to the radiation plate.

The entire wireless IC chip is preferably arranged such that the entirewireless IC chip is closer to the bottom surface of the recess than toan opening of the recess, the opening being provided near the first mainsurface of the substrate.

In this case, the wireless IC chip is completely housed in the recess,and thus, does not project from the substrate. For this reason, thewireless IC chip is less likely to be directly affected by externalshock, for example. Thus, the reliability of the wireless IC device isimproved.

A plurality of wedge members having different sizes when seen throughfrom a direction perpendicular to the bottom surface of the recess arepreferably provided. The wedge member that is larger is preferablydisposed in an area closer to the center of the bottom surface of therecess. The wedge member that is smaller is preferably disposed in anarea spaced away from the center of the bottom surface of the recess.

In this case, a larger wedge member is disposed in an area that iscloser to the center of the recess and where a greater amount ofprocessing deformation occurs and a larger amount of return deformationoccurs. Thus, the resistance to the return deformation is increased.This more effectively prevents deformation of the substrate near therecess.

The wireless IC device preferably further includes a protection filmarranged to cover the wireless IC chip mounted in the recess.

In this case, the wireless IC chip is protected from external moistureor toxic gases by the protection film. As a result, the reliability ofthe wireless IC device is further improved.

A method for manufacturing a wireless IC device according to a secondpreferred embodiment of the present invention is a method formanufacturing a wireless IC device including a radiation plate, awireless IC chip, and a substrate on which the wireless IC chip ismounted, the substrate being provided with a feed circuit, the feedcircuit including a resonant circuit and/or a matching circuit, theresonant circuit and/or the matching circuit including an inductanceelement, the feed circuit being electromagnetically coupled to theradiation plate. The method includes the steps of making a recess in thesubstrate made of a resin material by pressing a portion of a first mainsurface of the substrate and a portion of a wiring electrode, so thatthe wiring electrode extends along a bottom surface and an innercircumferential surface of the recess, the wiring electrode being formedin advance on the first main surface of the substrate and connected tothe feed circuit, forming a wedge member using a different material fromthe resin material such that the wedge member extends between the bottomsurface of the recess and a second main surface of the substrate apartfrom the wiring electrode, and mounting the wireless IC chip in therecess so as to couple the wireless IC chip to the wiring electrode.

By using this method, the recess is made by pressing the substrate. As aresult, the manufacturing cost is reduced. In addition, since the wiringelectrode is formed along the bottom surface and the innercircumferential surface of the recess, the length of the wiring routedbetween the wireless IC chip mounted in the recess and the first mainsurface of the substrate is reduced as much as possible. This preventsthe routed wiring from degrading the electrical properties.

A method for manufacturing a wireless IC device according to a thirdpreferred embodiment of the present invention is a method formanufacturing a wireless IC device including a radiation plate, awireless IC chip, and a substrate on which the wireless IC chip ismounted, the substrate being provided with a feed circuit, the feedcircuit including a resonant circuit and/or a matching circuit, theresonant circuit and/or the matching circuit including an inductanceelement, the feed circuit being electromagnetically coupled to theradiation plate. The method includes the steps of forming a wedge membersuch that the wedge member extends between a first main surface of thesubstrate made of a resin material and a second main surface thereofspaced apart from a wiring electrode, using a material that is differentfrom the resin material, the wiring electrode being formed in advance onthe first main surface of the substrate and connected to the feedcircuit, making a recess in the substrate by pressing a portion of thefirst main surface of the substrate, a portion of the wiring electrode,and the wedge member, so that the wiring electrode extends along abottom surface and an inner circumferential surface of the recess and sothat the wedge member extends between the bottom surface of the recessand the second main surface of the substrate, and mounting the wirelessIC chip in the recess so as to couple the wireless IC chip to the wiringelectrode.

By using this method, the wedge member is hardened while the recess isformed. Thus, the height of the recess is stabilized.

In addition, since the recess is made by pressing the substrate, themanufacturing cost is reduced. Also, since the wiring electrode isformed along the bottom surface and the inner circumferential surface ofthe recess, the length of the wiring routed between the wireless IC chipmounted in the recess and the first main surface of the substrate isreduced as much as possible. This prevents the routed wiring fromdegrading the electrical properties.

A method for manufacturing a wireless IC device according to a fourthpreferred embodiment of the present invention is a method formanufacturing a wireless IC device including a radiation plate, awireless IC chip, and a substrate on which the wireless IC chip ismounted, the substrate being provided with a feed circuit, the feedcircuit including a resonant circuit and/or a matching circuit, theresonant circuit and/or the matching circuit including an inductanceelement, the feed circuit being electromagnetically coupled to theradiation plate. The method includes the steps of forming a wedge membersuch that the wedge member extends between a first main surface of thesubstrate made of a resin material and a second main surface thereofspaced apart from a wiring electrode, using a different material fromthe resin material, the wiring electrode being formed in advance on thefirst main surface of the substrate and connected to the feed circuit,and making a recess, in which the wireless IC chip is to be embedded, inthe substrate by pressing the wireless IC chip against the first mainsurface of the substrate in a state in which the wireless IC chip ismounted on the first main surface of the substrate such that thewireless IC chip is opposed to the wiring electrode on the substrate, sothat the wiring electrode extends along a bottom surface and an innercircumferential surface of the recess and so that the wedge memberextends between the bottom surface of the recess and the second mainsurface of the substrate.

By using this method, the formation of the recess and the mounting ofthe wireless IC chip are performed in one step. Thus, the recess havinga stable depth is formed and the wireless IC chip is mounted stably.

In addition, since the recess is formed in the substrate by pressing thesubstrate via the wireless IC chip, the manufacturing cost is reduced.Also, since the wiring electrode is formed along the bottom surface andthe inner circumferential surface of the recess, the length of thewiring routed between the wireless IC chip mounted in the recess and thefirst main surface of the substrate is reduced as much as possible. Thisprevents the routed wiring from degrading the electrical properties.

In accordance with the various preferred embodiments of the presentinvention, the manufacturing cost of the wireless IC device is reducedand degradation of the electrical properties is prevented.

Other features, elements, arrangements, steps, processes,characteristics and advantages of the present invention will become moreapparent from the following detailed description of preferredembodiments of the present invention with reference to the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a wireless IC device according to a firstpreferred embodiment of the present invention.

FIGS. 2A to 2D are sectional views showing steps for manufacturing amodule according to the first preferred embodiment of the presentinvention.

FIG. 3 is a plan view of the bottom of a recess according to the firstpreferred embodiment of the present invention.

FIG. 4 is a plan view of the module according to the first preferredembodiment of the present invention.

FIGS. 5A to 5D are sectional views showing steps for manufacturing amodule according to a second preferred embodiment of the presentinvention.

FIG. 6 is a plan view of an area that will become the bottom of a recessaccording to the second preferred embodiment of the present invention.

FIGS. 7A to 7D are sectional views showing steps for manufacturing amodule according to a third preferred embodiment of the presentinvention.

FIG. 8 is a plan view of an area that will become the bottom of a recessaccording to the third preferred embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a substrate according toa fourth preferred embodiment of the present invention.

FIG. 10 is a diagram showing an electrical circuit formed in thesubstrate according to the fourth preferred embodiment of the presentinvention.

FIG. 11 is a sectional view of a wireless IC device according to amodification of a preferred embodiment of the present invention.

FIGS. 12A to 12C are sectional views showing steps for manufacturing asemiconductor apparatus according to the related art.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described withreference to FIGS. 1 to 11.

First Preferred Embodiment

A wireless IC device 10 according to a first preferred embodiment of thepresent invention will be described with reference to FIGS. 1 to 4.

As shown in a sectional view in FIG. 1, the wireless IC device 10 ispreferably formed by bonding a module 20, in which a wireless IC chip 30is mounted in a recess 21 of a substrate 22, to a radiation plate 14using a bonding material 16, such as an insulating adhesive sheet (anadhesive thin film on the adhesive surface of a commercially availableseal) or an adhesive, for example. The radiation plate 14 includes aconductive material that is arranged in a predetermined shape.

The radiation plate 14 may preferably be formed, for example, byprinting a resin including Ag particles on a sheet-shaped base andforming small wiring thereon by inkjet or photolithography and the basehaving the radiation plate 14 formed thereon may be bonded to acommodity, such as a package or container, for example.

While the radiation plate 14 is electromagnetically coupled to thesubstrate 22 via the insulating bonding material 16, a direct current isnot passed between the radiation plate 14 and the substrate 22.Specifically, the substrate 22 includes a coupling electrode, and theradiation plate 14 and the coupling electrode are electromagneticallycoupled via an electromagnetic wave. Also, the radiation plate 14 andthe coupling electrode may be electromagnetically coupled using only anelectrical field or a magnetic field.

If the wireless IC device 10 is used in an RFID system, an outsidereader/writer (not shown) communicates with the wireless IC chip 30 ofthe wireless IC device 10 bonded to a commodity via the radiation plate14 so as to read data stored in the wireless IC chip 30 in a contactlessmanner.

The substrate 22 is preferably made of a resin material, for example.The recess 21 is provided in the substrate 22 by pressing the substrate22. A wiring pattern 24 is provided along an upper surface 22 a, whichis a first main surface of the substrate 22, and an innercircumferential surface 21 t and a bottom surface 21 s of the recess 21.A wiring pattern 26 is provided along a lower surface 22 b, which is asecond main surface of the substrate 22.

FIG. 1 only shows through conductors 28 that pass between the bottomsurface 21 s of the recess 21 and the lower surface 22 b of thesubstrate 22 and are connected to the wiring patterns 24 and 26.However, as shown in FIG. 3, which is a plan view in which the recess 21is shown from above, the through conductors 28 are connected to twowiring patterns 24 b and 24 c of four wiring patterns 24 a to 24 dprovided on the bottom surface 21 s of the recess 21. Also, throughconductors 28 a and 28 b are provided at locations separate from thewiring patterns 24 a to 24 d. The through conductors 28 a and 28 b arewedge members and extend between the bottom surface 21 s of the recess21 and the lower surface 22 b of the substrate 22, similar to thethrough conductor 28 connected to the wiring patterns 24 b and 24 c.

In the module 20, as shown in a plan view in FIG. 4, the wireless ICchip 30 is mounted on the wiring patterns 24 a to 24 d provided on thebottom surface 21 s of the recess 21. The wireless IC chip 30 ispreferably mounted on the wiring patterns with bumps 12 (see FIG. 1)therebetween by flip-chip bonding using an Au bump, an Ag bump, a solderbump, or other suitable bump material or Ag nano-bonding, for example.The wireless IC chip 30 may be mounted using mold bonding or wirebonding or using a combination of these bonding methods, for example.Also, an insulating material may preferably be disposed between a mountelectrode of the wireless IC chip and the wiring patterns, and the mountelectrode and the wiring patterns may be electromagnetically coupledusing a capacitance or a magnetic field, for example.

An input/output terminal of the wireless IC chip 30 is connected to thewiring patterns 24 b and 24 c to which the through conductors 28 areconnected. A dummy terminal of the wireless IC chip 30 is connected tothe other wiring patterns 24 a and 24 d. The wiring patterns 24 b and 24c are electrically connected to feed circuits 26 s and 26 t defined bythe wiring pattern 26 on the lower surface 22 b of the substrate 22 viathe through conductors 28. Note that a portion of the wiring pattern 24(see FIG. 1) provided on the upper surface 22 a of the substrate 22 isnot shown in FIG. 4.

If the recess 21 is formed by pressing the substrate 22, the substrate22 may be return-deformed near the recess 21. The through conductors 28a and 28 b extending between the bottom surface 21 s of the recess 21and the lower surface 22 b of the substrate 22 prevent the substrate 22from being return-deformed near the recess 21.

In order to prevent the substrate 22 from being return-deformed near therecess 21, the through conductors 28, 28 a, and 28 b are preferably madeof a different material from that of the substrate 22. The throughconductors 28 a and 28 b may preferably be made of a nonconductivematerial, for example, since these conductors are not used forelectrical connection. However, if the same material as that used forthe through conductors 28 is used, the through conductors 28 a and 28 bcan be provided simultaneously with the through conductors 28. Thissimplifies the process to thereby reduce the manufacturing cost.

As shown in FIG. 3, the size of the through conductors 28, 28 a, and 28b, is increased closer to the center of the recess 21 is decreasedfarther from the center thereof. In the substrate 22, the amount ofprocessing deformation caused by a press is greater in an area closer tothe center of the recess 21, and the amount of processing deformationcaused by a press is less in an area farther away from the centerthereof. Therefore, an area having an increased processing deformationamount tends to be return-deformed to a greater extent after the press.Therefore, a larger through conductor is provided in an area that willbe return-deformed to a greater extent after the press so that returndeformation is more effectively prevented. This allows efficientformation of the through conductors using substantially the same amountof material.

Depending on the type of material, the size or shape of the recess,processing conditions, and other factors, an area closer to the innercircumferential surface of the recess 21 may be return-deformed to agreater extent after the substrate 22 is pressed and an area closer tothe center of the recess 21 may be return-deformed to a lesser extentafter the press. In such cases, it is preferable to provide a largerthrough conductor in an area closer to the inner circumferential surface21 t of the recess 21 and to provide a smaller through conductor in anarea closer to the center of the recess 21.

A portion of the wiring pattern 24 provided on the upper surface 22 a ofthe substrate 22 and the wiring pattern 26 provided on the lower surface22 b of the substrate 22 define a feed circuit including an inductanceelement. The feed circuit includes a resonant circuit having a resonantfrequency corresponding to the operating frequency of the wireless ICchip 30. The feed circuit may preferably include a matching circuitarranged to match the characteristic impedance of the radiation plate 14with that of the wireless IC chip 30.

Next, steps for manufacturing the module 20 will be described withreference to FIGS. 2A to 2D and FIG. 3. FIGS. 2A to 2D are sectionalviews schematically showing the steps for manufacturing the module 20.

First, as shown in FIG. 2A, a metal foil-attached resin sheet isprepared and the metal foil is processed into a predetermined pattern byetching or other suitable method. Thus, the wiring patterns 24 and 26made of the metal foil are formed on both surfaces or on one surface ofthe substrate 22 made of the resin sheet. The wiring pattern 24 formedon the upper surface 22 a of the substrate 22 is also formed in areasthat will become the bottom surface 21 s and inner circumferentialsurface 21 t of the recess 21 by a press in a subsequent process step.

A material that is relatively easy to process and that is deformed to alesser extent after being processed is suitable as the resin sheetsubstrate 22. For example, a resin sheet made of liquid crystal polymer(LCP), polyimide, or fluorocarbon resin is used as the substrate 22. Amaterial, such as copper, for example, that can easily be processed intoa wiring pattern is preferably used as the metal foil of the resinsheet.

Next, by pressing the upper surface 22 a of the resin sheet substrate 22as shown by an arrow 18 in FIG. 2A, the recess 21 is formed as shown inFIG. 2B. Simultaneously, portions of the wiring pattern 24 formed inadvance in the areas that will become the bottom surface 21 s and innercircumferential surface 21 t of the recess 21 are also pressed so thatthe portions are deformed into a shape extending along the bottomsurface 21 s and inner circumferential surface 21 t of the recess 21.These portions also define a wiring electrode.

For example, the recess 21 is made preferably by pressing a convex moldhaving a protrusion corresponding to the size and shape of the recess 21against the upper surface 22 a of the resin sheet substrate 22. Thesubstrate 22 may be heated as necessary and a recess may be formed bypressing the softened substrate 22. For example, a resin sheet isdisposed on a hot plate and heated to about 300° C. and a recess isformed on the resin sheet using a mold.

Next, as shown in FIG. 2C, through holes 28 s passing between the bottomsurface 21 s of the recess 21 and the lower surface 22 b of thesubstrate 22 are formed by laser processing, punching using a mold, orother suitable method. Subsequently, the through conductors 28 areformed preferably by filling the through holes 28 s with a conductivematerial, such as a via paste, for example.

As shown in FIG. 3, at the same time that the through conductors 28connected the wiring patterns 24 b and 24 c are formed, the throughconductors 28 a and 28 b are formed at locations separate from thewiring patterns 24 a to 24 d. The through conductors 28 a and 28 b arewedge members.

The through holes 28 s for forming the through conductors 28 and throughholes for forming the through conductors 28 a and 28 b may be formedfrom the bottom surface 21 s side of the recess 21 or from the lowersurface 22 b side of the resin sheet substrate 22.

Next, as shown in FIG. 2D, the wireless IC chip 30 is mounted in therecess 21. That is, terminals of the wireless IC chip 30 are preferablyelectrically connected to portions of the wiring pattern 24 on thebottom surface 21 s of the recess 21 via the solder bumps 12.

If multiple modules 20 are manufactured simultaneously, the resin sheetsubstrate 22 is cut into individual modules 20.

According to the above-described process, the recess 21 is easily formedby pressing the resin sheet substrate 22. As a result, the cost of themodule 20 is reduced. In addition, the module 20 having a thicknessapproximately equal to that of the wireless IC chip 30 is manufactured.Therefore, the profile of the module 20 is advantageously reduced.

Also, the through conductors 28, 28 a, and 28 b extending between thelower surface 22 b of the resin sheet substrate 22 and the bottomsurface 21 s of the recess 21 prevent deformation of portions close tothe interface with the through conductors 28, 28 a, and 28 b, of theresin sheet substrate 22. This prevents return-deformation of portionsclose to the recess 21, of the substrate 22.

Second Preferred Embodiment

A wireless IC device according to a second preferred embodiment of thepresent invention will be described with reference to FIGS. 5A to 5D andFIG. 6.

The wireless IC device according to the second preferred embodiment hasa configuration substantially the same as that of the wireless IC deviceaccording to the first preferred embodiment. The difference between thesecond preferred embodiment and first preferred embodiment will bedescribed and the same reference numerals will be assigned to the sameor similar elements.

The wireless IC device according to the second preferred embodiment isdifferent from the first preferred embodiment in the order of the stepsfor manufacturing the module. Hereafter, the steps for manufacturing themodule will be described with reference to sectional views in FIGS. 5Ato 5D and a main portion plan view in FIG. 6.

First, as shown in FIG. 5A, a metal foil-attached resin sheet isprepared and the metal foil is processed into a predetermined pattern byetching or other suitable method. Thus, the wiring patterns 24 and 26are formed on both or one of the surfaces 22 a and 22 b of the substrate22 made of the resin sheet. The wiring pattern 24 formed on the uppersurface 22 a of the substrate 22 including in areas that will become thebottom surface 21 s and inner circumferential surface 21 t of the recess21 by a press in a subsequent process.

A material that is relatively easy to process and that is deformed to alesser extent after processed is suitable as the resin sheet substrate22. For example, a resin sheet made of liquid crystal polymer (LCP),polyimide, or fluorocarbon resin, for example, is preferably used as thesubstrate 22. A material, such as copper, for example, that is easilyprocessed into a wiring pattern is preferably used as the metal foil ofthe resin sheet.

Next, as shown in FIG. 5B, through holes 28 t passing through thesurfaces 22 a and 22 b of the resin sheet substrate 22 are formed bylaser processing, punching using a mold, or other suitable method. Then,through conductors 28 x are formed by filling the through holes 28 twith a conductive material such as a via paste, for example.

At that time, as shown in FIG. 6, the through conductors 28 x are formedso that the through conductors 28 x are connected to the two wiringpatterns 24 b and 24 c of the wiring the patterns 24 a to 24 d formed inadvance in an area 21 x that will become the bottom surface 21 s of therecess 21. Simultaneously, through conductors 28 p and 28 q are formedat locations separate from the wiring patterns 24 a to 24 d.

The through holes 28 t arranged to form the through conductors 28 x andthrough holes arranged to form the through conductors 28 p and 28 q maybe formed to extend from the upper surface 22 a side of the resin sheetsubstrate 22 or from the lower surface 22 b side thereof.

Next, by pressing the upper surface 22 a of the resin sheet substrate 22as shown by an arrow 18 a in FIG. 5C, the recess 21 is formed.Simultaneously, portions of the wiring pattern 24 that are formed inadvance in areas that will become the bottom surface 21 s and innercircumferential surface 21 t of the recess 21, are also pressed so thatthe portions are formed into a shape extending along the bottom surface21 s and inner circumferential surface 21 t of the recess 21, and definea wiring electrode.

Simultaneously, the through conductors 28 x, 28 p, and 28 q (see FIG. 6)are also pressed and deformed so that the conductors 28 x 28 p, and 28 qextend between the bottom surface 21 s of the recess 21 and the lowersurface 22 b of the substrate 22. The through conductors 28 p and 28 qare wedge members and are separate from the wiring pattern 24 (24 a to24 d).

The recess 21 is preferably formed, for example, by pressing a convexmold having a protrusion corresponding to the size and shape of therecess 21 against the upper surface 22 a of the resin sheet substrate22. The substrate 22 may be heated and a recess may be formed bypressing the softened substrate 22. For example, a resin sheet isdisposed on a hot plate and a mold is pressed against the resin sheet.

Next, as shown in FIG. 5D, the wireless IC chip 30 is mounted in therecess 21. Specifically, terminals of the wireless IC chip 30 arepreferably electrically connected to portions of the wiring pattern 24formed on the bottom surface 21 s of the recess 21 via the bumps 12, forexample.

If multiple modules 20 are manufactured simultaneously, the resin sheetsubstrate 22 is cut into individual modules 20.

By performing the above-described process, the through conductors 28 x,28 p, and 28 q are hardened while the recess 21 is formed. Thus, theheight of the recess 21 is stabilized.

Also, as in the first preferred embodiment, the recess 21 is easilyformed by pressing the resin sheet substrate 22. As a result, the costof the module 20 is reduced. Also, the module 20 having a thicknessapproximately the same as that of the wireless IC chip 30 ismanufactured. Therefore, the profile of the module 20 is reduced.

In addition, the wiring pattern 24 is easily formed on the innercircumferential surface 21 t and bottom surface 21 s of the recess 21.Thus, the length of the wiring between the wireless IC chip 30 mountedon the recess 21 and the upper surface 22 a of the substrate 22 is asshort as possible. As a result, the wiring is not routed through adetour on the lower surface 22 b of the substrate 22. That is,electrical properties are not degraded due to the occurrence of anunnecessary inductor component or capacitor component in the detourportion of the wiring, and thus, the manufacturing cost is increased.

Also, the through conductors 28 x, 28 p, and 28 q extending between thelower surface 22 b of the resin sheet substrate 22 and the bottomsurface 21 s of the recess 21 prevent deformation of portions close tothe interface with the through conductors 28 x, 28 p, and 28 q, of theresin sheet substrate 22. This prevents return-deformation of thesubstrate 22 near the recess 21.

Third Preferred Embodiment

A wireless IC device according to a third preferred embodiment of thepresent invention will be described with reference to FIGS. 7A to 7D andFIG. 8.

The wireless IC device according to the third preferred embodiment has aconfiguration substantially the same as that of the wireless IC deviceaccording to the first preferred embodiment. The wireless IC deviceaccording to the third preferred embodiment is different from the firstpreferred embodiment in the order of the steps for manufacturing themodule 20. Hereafter, the steps for manufacturing the module 20 will bedescribed with reference to a sectional views in FIGS. 7A to 7D and amain portion plan view shown in FIG. 8.

First, as shown in FIG. 7A, a metal foil-attached resin sheet isprepared and the metal foil is processed into a predetermined pattern byetching or other suitable method. Thus, the wiring patterns 24 and 26are formed on both or one of the surfaces 22 a and 22 b of the resinsheet substrate 22. A material that is easy to process and is deformedto a lesser extent after processed is suitable as the resin sheetsubstrate 22. For example, a resin sheet made of liquid crystal polymer(LCP), polyimide, or fluorocarbon resin, for example, is preferably usedas the substrate 22. A material, such as copper, for example, that iseasily processed into a wiring pattern is preferably used as the metalfoil of the resin sheet.

Next, as shown in FIG. 7B, the through holes 28 t passing between thesurfaces 22 a and 22 b of the resin sheet substrate 22 are formed bylaser processing, punching using a mold, or other suitable method. Then,the through conductors 28 x are formed by filling the through holes 28 twith a conductive material such as a via paste, for example.

At that time, as shown in FIG. 8, the through conductors 28 x are formedso that the through conductors 28 x are connected to the two wiringpatterns 24 b and 24 c of the wiring patterns 24 a to 24 d formed inadvance in the area 21 x that will become the bottom surface 21 s of therecess 21. Simultaneously, the through conductors 28 p and 28 q areformed at locations separate from the wiring patterns 24 a to 24 d.

The through holes 28 t arranged to form the through conductors 28 x andthrough holes arranged to form the through conductors 28 p and 28 q maypreferably be formed from the upper surface 22 a side of the resin sheetsubstrate 22 or from the lower surface 22 b side thereof.

Next, as shown in FIG. 7C, the wireless IC chip 30 is disposed in anarea that will become the bottom surface 21 s of the recess 21.Specifically, the wireless IC chip 30 is disposed on the wiring pattern24 in the area that will become the bottom surface 21 s of the recess 21with the bumps 12 made of a conductive paste therebetween. Then, asshown by an arrow 18 b in FIG. 7D, by pressing the wireless IC chip 30disposed on the upper surface 22 a of the resin sheet substrate 22 usinga flat plate, the recess 21 is formed in the resin sheet substrate 22.Simultaneously, the wireless IC chip 30 is embedded in the recess 21.

At this time, portions of the wiring pattern formed in advance in areasthat will become the bottom surface 21 s and inner circumferentialsurface 21 t of the recess 21 are also pressed so that the portions areformed into a shape extending along the bottom surface 21 s and innercircumferential surface 21 t of the recess 21, and define a wiringelectrode.

In addition, the through conductors 28 x, 28 p, and 28 q (see FIG. 8)are pressed and deformed so that the through conductors 28 x, 28 p, and28 q extend between the bottom surface 21 s of the recess 21 and thelower surface 22 b of the substrate 22. The through conductors 28 p and28 q are wedge members and are separate from the wiring pattern 24 (24 ato 24 d).

By raising the temperature of the resin sheet substrate 22 at the timeof the press, for example, by placing the substrate 22 on a hot plate,so that the via paste forming the through conductors 28 x and the bumps12 (conductive paste, etc.) for mounting the wireless IC chip 30 arehardened, the processes of forming the recess 21 and mounting thewireless IC chip 30 are simultaneously completed.

If multiple modules 20 are manufactured simultaneously, the resin sheetsubstrate 22 is cut into individual modules 20.

By performing the above-described process, the bumps arranged to mountthe wireless IC chip 30 are formed and the via paste filling the throughholes 28 t are hardened while the recess 21 is formed. This enablesforming the recess 21 having a stable depth and mounting the wireless ICchip 30 in one process step.

Also, as in the first preferred embodiment, the recess 21 is easilyformed by pressing the resin sheet substrate 22. As a result, the costof the module 20 is reduced. In addition, the module 20 having athickness approximately equal to that of the wireless IC chip 30 ismanufactured. Therefore, the profile of the module 20 is reduced.

Also, the wiring pattern 24 is easily formed on the innercircumferential surface 21 t and bottom surface 21 s of the recess 21.Thus, the length of the wiring between the wireless IC chip 30 mountedon the recess 21 and the upper surface 22 a of the substrate 22 is asshort as possible. As a result, the wiring is not routed through adetour on the lower surface 22 b of the substrate 22. That is, theelectrical properties are not degraded due to the occurrence of anunnecessary inductor component or capacitor component in the detourportion of the wiring, and thus, the manufacturing cost is increased.

Also, the through conductors 28 x, 28 p, and 28 q extending between thelower surface 22 b of the resin sheet substrate 22 and the bottomsurface 21 s of the recess 21 prevent deformation of portions close tothe interface with the through conductors 28 x, 28 p, and 28 q, of theresin sheet substrate 22. This prevents return-deformation of thesubstrate 22 near the recess 21.

Fourth Preferred Embodiment

An wireless IC device according to a fourth preferred embodiment of thepresent invention will be described with reference to FIGS. 9 and 10.

The wireless IC device according to the fourth preferred embodiment isdifferent from the first preferred embodiment in that the substrate is amultilayer resin substrate.

As shown in an exploded plan view in FIG. 9, the substrate of thewireless IC device according to the fourth preferred embodiment isformed by sequentially laminating four resin substrates 35 to 38, forexample.

On the upper surface of the resin substrate 35, electrodes 40, 42, 44,and 46 arranged to mount a wireless IC chip and wiring patterns 41 and43, ends of which are connected to the mount electrodes 40 and 42, areformed. In addition, through holes 80 and 90 are provided at the otherends of the wiring patterns 41 and 43 on the resin substrate 35.

On the upper surface of the resin substrate 36, an approximatelyS-shaped wiring pattern 50 is provided. Also, on the resin substrate 36,through holes 81 and 91 are provided at both ends of the wiring pattern50 and through holes 82 and 92 are arranged so as to be spaced apartfrom the wiring pattern 50.

On the upper surface of the resin substrate 36, two spiral wiringpatterns 60 and 62 are provided. Also, on the resin substrate 36,through holes 83 and 93 are provided at ends of the wiring patterns 60and 62, respectively, and through holes 84 and 94 are arranged so as tobe spaced apart from the wiring patterns 60 and 62.

On the upper surface of the resin substrate 38, two spiral wiringpatterns 70 and 72 are provided.

After the through holes 80 to 84 and 90 to 94 are filled with a viapaste, the resin substrates 35 to 38 are laminated. Then, throughconductors are formed in the through holes 80 to 84 and 90 to 94.

When the resin substrates 35 and 38 are laminated, the through holes 80,82, and 84 communicate with one another. The through conductors formedin the through holes 80, 82, and 84 electrically connect the other endsof the wiring patterns 41 and 43 on the resin substrate 35, and ends 70a and 72 a of the wiring patterns 70 and 72 on the resin substrate 38.

The other ends 70 b and 72 b of the wiring patterns 70 and 72 on theresin substrate 38 are connected to ends of the wiring patterns 60 and62 provided on the resin substrate 37 via the through conductors formedin the through holes 83 and 93 of the resin substrate 37.

The other ends 60 a and 62 a of the wiring patterns 60 and 62 providedon the resin substrate 37 are connected to both ends of the wiringpattern 50 provided on the resin substrate 36 via the through conductorsformed in the through holes 81 and 91 of the resin substrate 36.

FIG. 10 is a diagram showing an electrical circuit provided in thesubstrate by laminating the resin substrates 35 to 38. Two inductanceelements L₁ and L₂ are connected in series between terminals P1 and P2corresponding to the mount substrates 40 and 42. The inductance L₁ isdefined by the wiring patterns 50, 60, and 70 on the left hand side ofFIG. 9. The inductance L₂ is defined by the wiring patterns 50, 62, and72 on the right hand side of FIG. 9.

On the substrate including the laminated resin substrates 35 to 38, arecess is formed by pressing an area 21 y that is shown by a chain linein FIG. 9 and that includes the mount electrodes 40, 42, 44, and 46.Then, a wireless IC chip is mounted on the mount electrodes 40, 42, 44,and 46.

Alternatively, on the substrate including the laminated resin substrates35 to 38, a recess is formed by disposing a wireless IC chip on themount electrodes 40, 42, 44, and 46 and then pressing the wireless ICchip using a flat plate. Thus, the wireless IC chip is embedded in therecess.

By forming a recess by pressing a multilayer resin substrate, themanufacturing cost is reduced. In addition, by using the wiring patterns41 and 43 provided on the upper surface of the resin substrate 35, thelength of the wiring routed between the wireless IC chip mounted in therecess and the upper surface of the multilayer resin substrate isreduced as much as possible. This prevents the routed wiring fromdegrading the electrical properties.

Modification 1

A wireless IC device 11 according to a modification of a preferredembodiment of the present invention will be described with reference toa sectional view in FIG. 11.

As shown in FIG. 11, the wireless IC device 11 according to themodification includes a protection film 32 in addition to theconfiguration of the first preferred embodiment. Specifically, theprotection film 32 arranged to cover the wireless IC chip 30 mounted inthe recess 21 is formed by filling the recess 21 with a resin.

Since the wireless IC chip 30 is protected from external moisture, toxicgases, and other contaminants by the protection film 32, the reliabilityof the wireless IC device 11 is further enhanced.

As is understood from the description above, by forming the recess bypressing the resin substrate, the manufacturing cost of the wireless ICdevice is reduced. In addition, since the length of the wiringconnecting between the wireless IC chip mounted in the recess and theupper surface of the substrate is reduced as much as possible,degradation of the electrical properties is prevented.

The present invention is not limited to the above-described preferredembodiments and various changes can be made thereto.

For example, each through conductor (wedge member) may include sectionshaving a uniform size or may include sections having different sizes.Each through conductor (wedge member) may have a wedge shape in which asection at one end is the largest and a second at the other end is thesmallest.

While preferred embodiments of the invention have been described above,it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the invention. The scope of the invention, therefore, isto be determined solely by the following claims.

1. A wireless IC device comprising: a radiation plate; a wireless ICchip; and a substrate on which the wireless IC chip is mounted, thesubstrate being provided with a feed circuit, the feed circuit includingat least one of a resonant circuit or a matching circuit, the at leastone of the resonant circuit or the matching circuit including aninductance element, the feed circuit being electromagnetically coupledto the radiation plate; wherein the substrate is made of a resinmaterial and includes a recess in a first main surface thereof; thesubstrate is provided with a wiring electrode arranged along a bottomsurface and an inner circumferential surface of the recess and on thefirst main surface of the substrate, the wiring electrode beingelectrically connected to the feed circuit; the substrate is providedwith a wedge member made of a different material from that of the resinmaterial, the wedge member extending between the bottom surface of therecess and a second main surface of the substrate so as to be spacedapart from the wiring electrode; the wireless IC chip is mounted in therecess and coupled to the wiring electrode; and the wedge member isarranged to prevent return-deformation of portions of the substrateclose to the recess.
 2. The wireless IC device according to claim 1,wherein the wedge member is defined by a through hole passing throughthe substrate that is filled with a conductive material.
 3. The wirelessIC device according to claim 1, wherein the feed circuit is provided onat least one of the first main surface of the substrate or the secondmain surface thereof.
 4. The wireless IC device according to claim 1,wherein the wireless IC chip is arranged such that the entire wirelessIC chip is closer to the bottom surface of the recess than to an openingof the recess, the opening being provided in the first main surface ofthe substrate.
 5. The wireless IC device according to claim 1, wherein aplurality of the wedge members are provided and have different sizes;and a size of a first wedge member of the plurality of wedge membersthat is disposed close to a center of the bottom surface of the recessis larger than a size of a second wedge member of the plurality of wedgemembers that is disposed farther from the center of the bottom surfaceof the recess.
 6. The wireless IC device according to claim 1, furthercomprising a protection film arranged to cover the wireless IC chipmounted in the recess.
 7. A method for manufacturing a wireless ICdevice including a radiation plate, a wireless IC chip, and a substrateon which the wireless IC chip is mounted, the substrate being providedwith a feed circuit, the feed circuit including at least one of aresonant circuit or a matching circuit, the at least one of the resonantcircuit or the matching circuit including an inductance element, thefeed circuit being electromagnetically coupled to the radiation plate,the method comprising the steps of: forming a recess in the substratemade of a resin material by pressing a portion of a first main surfaceof the substrate and a portion of a wiring electrode, so that the wiringelectrode extends along a bottom surface and an inner circumferentialsurface of the recess, the wiring electrode being formed in advance onthe first main surface of the substrate and connected to the feedcircuit; forming a wedge member using a different material from theresin material such that the wedge member extends between the bottomsurface of the recess and a second main surface of the substrate spacedapart from the wiring electrode; and mounting the wireless IC chip inthe recess so as to couple the wireless IC chip to the wiring electrode;wherein the wedge member is arranged to prevent return-deformation ofportions of the substrate close to the recess.
 8. A method formanufacturing a wireless IC device including a radiation plate, awireless IC chip, and a substrate on which the wireless IC chip ismounted, the substrate being provided with a feed circuit, the feedcircuit including at least one of a resonant circuit or a matchingcircuit, the at least one of the resonant circuit or the matchingcircuit including an inductance element, the feed circuit beingelectromagnetically coupled to the radiation plate, the methodcomprising the steps of: forming a wedge member such that the wedgemember extends between a first main surface of the substrate made of aresin material and a second main surface thereof spaced apart from awiring electrode, the wiring electrode being formed in advance on thefirst main surface of the substrate and connected to the feed circuit,using a different material from the resin material; forming a recess inthe substrate by pressing a portion of the first main surface of thesubstrate, a portion of the wiring electrode, and the wedge member, sothat the wiring electrode extends along a bottom surface and an innercircumferential surface of the recess and so that the wedge memberextends between the bottom surface of the recess and the second mainsurface of the substrate; and mounting the wireless IC chip in therecess so as to couple the wireless IC chip to the wiring electrode;wherein the wedge member is arranged to prevent return-deformation ofportions of the substrate close to the recess.
 9. A method formanufacturing a wireless IC device including a radiation plate, awireless IC chip, and a substrate on which the wireless IC chip ismounted, the substrate being provided with a feed circuit, the feedcircuit including at least one of a resonant circuit or a matchingcircuit, the at least one of the resonant circuit or the matchingcircuit including an inductance element, the feed circuit beingelectromagnetically coupled to the radiation plate, the methodcomprising the steps of: forming a wedge member such that the wedgemember extends between a first main surface of the substrate made of aresin material and a second main surface thereof spaced apart from awiring electrode, using a different material different from the resinmaterial, the wiring electrode being formed in advance on the first mainsurface of the substrate and connected to the feed circuit; and forminga recess, in which the wireless IC chip is to be embedded, on thesubstrate by pressing the wireless IC chip against the first mainsurface of the substrate in a state in which the wireless IC chip ismounted on the first main surface of the substrate such that thewireless IC chip is opposed to the wiring electrode on the substrate, sothat the wiring electrode extends along a bottom surface and an innercircumferential surface of the recess, and so that the wedge memberextends between the bottom surface of the recess and the second mainsurface of the substrate; wherein the wedge member is arranged toprevent return-deformation of portions of the substrate close to therecess.
 10. A wireless IC device comprising: a radiation plate; awireless IC chip; and a substrate on which the wireless IC chip ismounted, the substrate being provided with a feed circuit, the feedcircuit including at least one of a resonant circuit or a matchingcircuit, the at least one of the resonant circuit or the matchingcircuit including an inductance element, the feed circuit beingelectromagnetically coupled to the radiation plate; wherein thesubstrate is made of a resin material and includes a recess in a firstmain surface thereof; the substrate is provided with a wiring electrodearranged along a bottom surface of the recess and on the first mainsurface of the substrate, the wiring electrode being electricallyconnected to the feed circuit; the substrate is provided with a wedgemember made of a different material from that of the resin material, thewedge member extending between the bottom surface of the recess and asecond main surface of the substrate so as to be spaced apart from thewiring electrode; the wireless IC chip is mounted in the recess andcoupled to the wiring electrode; and the wedge member is arranged toprevent return-deformation of portions of the substrate close to therecess.
 11. The wireless IC device according to claim 10, wherein thewedge member is defined by a through hole passing through the substratethat is filled with a conductive material.
 12. The wireless IC deviceaccording to claim 10, wherein the feed circuit is provided on at leastone of the first main surface of the substrate or the second mainsurface thereof.
 13. The wireless IC device according to claim 10,wherein the wireless IC chip is arranged such that the entire wirelessIC chip is closer to the bottom surface of the recess than to an openingof the recess, the opening being provided in the first main surface ofthe substrate.
 14. The wireless IC device according to claim 10, whereina plurality of the wedge members are provided and have different sizes;and a size of a first wedge member of the plurality of wedge membersthat is disposed close to a center of the bottom surface of the recessis larger than a size of a second wedge member of the plurality of wedgemembers that is disposed farther from the center of the bottom surfaceof the recess.
 15. The wireless IC device according to claim 10, furthercomprising a protection film arranged to cover the wireless IC chipmounted in the recess.
 16. A method for manufacturing a wireless ICdevice including a radiation plate, a wireless IC chip, and a substrateon which the wireless IC chip is mounted, the substrate being providedwith a feed circuit, the feed circuit including at least one of aresonant circuit or a matching circuit, the at least one of the resonantcircuit or the matching circuit including an inductance element, thefeed circuit being electromagnetically coupled to the radiation plate,the method comprising the steps of: forming a recess in the substratemade of a resin material by pressing a portion of a first main surfaceof the substrate and a portion of a wiring electrode, so that the wiringelectrode extends along a bottom surface of the recess, the wiringelectrode being formed in advance on the first main surface of thesubstrate and connected to the feed circuit; forming a wedge memberusing a different material from the resin material such that the wedgemember extends between the bottom surface of the recess and a secondmain surface of the substrate spaced apart from the wiring electrode;and mounting the wireless IC chip in the recess so as to couple thewireless IC chip to the wiring electrode; wherein the wedge member isarranged to prevent return-deformation of portions of the substrateclose to the recess.
 17. A method for manufacturing a wireless IC deviceincluding a radiation plate, a wireless IC chip, and a substrate onwhich the wireless IC chip is mounted, the substrate being provided witha feed circuit, the feed circuit including at least one of a resonantcircuit or a matching circuit, the at least one of the resonant circuitor the matching circuit including an inductance element, the feedcircuit being electromagnetically coupled to the radiation plate, themethod comprising the steps of: forming a wedge member such that thewedge member extends between a first main surface of the substrate madeof a resin material and a second main surface thereof spaced apart froma wiring electrode, the wiring electrode being formed in advance on thefirst main surface of the substrate and connected to the feed circuit,using a different material from the resin material; forming a recess inthe substrate by pressing a portion of the first main surface of thesubstrate, a portion of the wiring electrode, and the wedge member, sothat the wiring electrode extends along a bottom surface of the recessand so that the wedge member extends between the bottom surface of therecess and the second main surface of the substrate; and mounting thewireless IC chip in the recess so as to couple the wireless IC chip tothe wiring electrode; wherein the wedge member is arranged to preventreturn-deformation of portions of the substrate close to the recess. 18.A method for manufacturing a wireless IC device including a radiationplate, a wireless IC chip, and a substrate on which the wireless IC chipis mounted, the substrate being provided with a feed circuit, the feedcircuit including at least one of a resonant circuit or a matchingcircuit, the at least one of the resonant circuit or the matchingcircuit including an inductance element, the feed circuit beingelectromagnetically coupled to the radiation plate, the methodcomprising the steps of: forming a wedge member such that the wedgemember extends between a first main surface of the substrate made of aresin material and a second main surface thereof spaced apart from awiring electrode, using a different material different from the resinmaterial, the wiring electrode being formed in advance on the first mainsurface of the substrate and connected to the feed circuit; and forminga recess, in which the wireless IC chip is to be embedded, on thesubstrate by pressing the wireless IC chip against the first mainsurface of the substrate in a state in which the wireless IC chip ismounted on the first main surface of the substrate such that thewireless IC chip is opposed to the wiring electrode on the substrate, sothat the wiring electrode extends along a bottom surface of the recess,and so that the wedge member extends between the bottom surface of therecess and the second main surface of the substrate; wherein the wedgemember is arranged to prevent return-deformation of portions of thesubstrate close to the recess.